Jet propulsion underwater - How to create bubbles
First, create a single bubble by making a sphere and making it a glass material, or however you want the bubble to look.

Add a particle system to the engine and under render, change the default halo to object, and under object, select your bubble


To make each of the bubbles a different size, change the scale randomness to something higher like 1.



To change the velocity of the bubbles, change the direction you want them to flow under the velocity tab.



There are many more settings you can change like turning gravity on and off. Good Luck!